| タイトル | The impact of mass extinctions |
| 本文（外部サイト） | http://hdl.handle.net/2060/19890011944 |
| 著者（英） | Flessa, Karl W. |
| 著者所属（英） | Arizona Univ.|National Science Foundation |
| 発行日 | 1988-01-01 |
| 言語 | eng |
| 内容記述 | In the years since Snowbird an explosive growth of research on the patterns, causes, and consequences of extinction was seen. The fossil record of extinction is better known, stratigraphic sections were scrutinized in great detail, and additional markers of environmental change were discovered in the rock record. However flawed, the fossil record is the only record that exists of natural extinction. Compilations from the primary literature contain a faint periodic signal: the extinctions of the past 250 my may be regulary spaced. The reality of the periodicity remains a subject for debate. The implications of periodicity are so profound that the debate is sure to continue. The greater precision from stratigraphic sections spanning extinction events has yet to resolve controversies concerning the rates at which extinctions occurred. Some sections seem to record sudden terminations, while others suggest gradual or steplike environmental deterioration. Unfortunately, the manner in which the strata record extinctions and compile stratigraphic ranges makes a strictly literal reading of the fossil record inadvisable. Much progress was made in the study of mass extinctions. The issues are more sharply defined but they are not fully resolved. Scenarios should look back to the phenomena they purport to explain - not just an iridium-rich layer, but the complex fabric of a mass extinction. |
| NASA分類 | ENVIRONMENT POLLUTION |
| レポートNO | 89N21315 |
| 権利 | No Copyright |
| URI | https://repository.exst.jaxa.jp/dspace/handle/a-is/142543 |
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